Process of preparing cellulose esters in definite forms.



LEONHARD LEDERER, OF SULZBAGH, GERMANY.

PROCESS FOR PREPARING CELLULOSE ESTERS IN DEFINITE FORMS.

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T 0 all whom it may concern:

Be it known that I, LEONHARD LEDERER, a subject of the Emperor of Germany, residing at Sulzbach', Germany, have invented a certain new and useful Process for Preparing Cellulose Esters in Definite Forms, of which the following is a specification.

In esterifying cellulose by means of or ganic acid chlorids or anhydrids a fluid mass is generally obtained as the product of the reactions, from which the cellulose-esters must then be separated. This can be avoided and the esters obtained immediately in a solid form, if the acidifying process is car ried out in the presence of a substance which does not dissolve acidified cellulose. F or this purpose carbon tetrachlorid has been found exceedingly well adapted, being not only cheap but also possessing the highly estimable advantage above the diluent used for similar purposes French patent specification 347,906) of not being combustible and at the same time having a boiling point sufficiently different from that of the fatty acids and their anhydrids to enable a separation and recovery of the various fluid substances to be effected without difficulty. The use of carbon tetrachlorid was however not immediately to be expected. As is well-known, cellulose acetates dissolve in acetic acid, chloroform and tetrachlorethane. Owing to the close relationship of the two last-named substances to carbon tetrachlorid the assumption was justified that carbon tetrachlorid would also take up cellulose. In reality however this promising assumption does not hold good. i

Example: In order to obtain say cellulose acetate in the form of cotton, one proceeds for instance, in such a manner that the cotton is first hydrolyzed with an equal weight of glacial acetic acid containing 2-} per cent. of sulfuric acid, then three times the weight of carbon tetrachlorid is added and the cellulose acet-ylized with 31} times the weight of acetic anhydrid, which has been diluted with an equal weight of carbon tetrachlorid. At ordinary temperature the hydrolyzation requires from 12 to 24 hours, and an equal space of time is occupied by the acetylization; at a higher temperature less time is required for both processes. After the reaction is completed, the cellulose acetate, which has the structure of the starting material, is separated from the fluid mass by pressing or by centrifugalforce and freed from acid in the usual way by washing with alcohol or water. In a similar manner, yarn, fabrics and other objects consisting of pure cellulose or mixed with other fibrous mate rials may be acetylized.

The products obtained as described are sparingly and incompletely soluble in chloroform, but easily soluble in chloroform containing alcohol. If filaments treated by the new process are woven together with other textile fibers, and the woven fabric thus produced is dyed, special color effects may be produced, because the products olr tained according to the present application will not readily absorb coloring matter.

In treating cotton by my present process, the process may be conducted in such a manner, that acetylization takes place throughout the thickness of the raw material, or so as to leave a core of untreated cotton fiber.

For producing other fatty acid esters, such as the esters of propionic or butyric acid, corresponding quantities ofthe necessary acid anhydrids, say 4%- parts by weight of propionic anhydrid or 5.6 parts of butyric anhydrid, are employed instead of acetic anhydrid, and in other respects the process 'iscarried out as described above.

WVhat I claim is The process for obtaining cellulose esters in the same physical form as the raw material employed, which consists in first hydrolyzing cellulose by treating it with a hydrolyzing agent, esterifying the hydrocellulose thus produced by causing the anhydrid of the acid employed to act .on the same in the presence of carbon tetrachlorid, mechani ca-lly separating the product from the accompanying liquid and then Washing 1t, substantially as described.

In witness whereof I have hereunto set my hand in the presence of two witnesses.

Witnesses I PAUL CUBAsoH,

J OHANN STRoBEL.

Patented Aug. 1, 1911.

Application filed November 30, 1906. Serial No. 345,776. (Specimens) 

